Kristjana II succeeded her enigmatic mother Thorey III in 1261. Her reign began with a less than auspicious event: the sacking of Fjallasay by Algonquins. The earls, with almost all their energies ploughed into expanding their own holdings in the Hafsvaedaland, had no response to the attack.

Kristjana moved her court, at potentially great personal risk to Fjallasay in 1264. This not only focussed attention on the strategically placed island but allowed the Althing far out in Isafjordhur more freedom of movement and kept it out of the hands of the earls. She imposed the role of the itinerant courts on the new lands undermining the earls' rights and then, when they complained, she outlawed them for dereliction of duty and this led to a minor civil war between the crown and the Earl of Kyreyja. However this was patched up after Kyreyja paid homage to Kristjana, handing her a sliver of land in the Hafsvaedaland (now site of the town of Ámjogrunna). She also commissioned the Hafsvaedalandtakabok which would properly detail everyone's holdings in the area. A shrewd move, it not only kept the earls onside by ratifying their conquests but it also detailed how many farms, forts and actual settlers there were: vital if the Althing was to get its share of the taxes. Finally, with Fjallasay rebuilding and filling with merchants eager to exploit the opening passages to the west, Kristjana negotiated the permanent crown duty on furs passing through the Breidurass.

Even though the rule of the Althing had intruded into their new lands the earls kept themselves self-interested. Indeed they seemed to multiply; Karantóborg was founded in 1270, Logáyfir in 1272 and Gudnýborg in 1278 and each soon had its own lord operating largely independently from the earls. They would routinely ignore war bands headed for other earls' holdings, even allowing a second attempted storming of Fjallasay in 1275. Eventually the Althing came to the conclusion the only way to control them was to beat them at their own game. The normally tax-averse Althing agreed to collect an extraordinary tithe and in 1279 an Icelandic army was contracted for five season's campaigning. At 500-800 men this vastly outnumbered the warbands normally raised by the earls and required a huge store of food to be moved to Greenland to help supply the men on their transport. The bold move did not go unnoticed by the earls but there was little they could do. With the Althing's troops assisting them the army could easily reduce the earls' old strongholds in the east.

Kristjana died suddenly in September 1280 and would not get to see her army's success, nor the dramatic growth in crown land. Kristjana had never formally proclaimed her successor but it probably was assumed that either one of her daughters would have succeeded. However, in a measure of the Althing's newly found power and confidence it intervened in the succession; instead it elected their cousin, Thyri to the throne.